Who should pay processing fee?

As a cryptocurrency enthusiast and investor, I often find myself wondering about the intricacies of transactions and fees. One particular question that has arisen is regarding who should bear the responsibility of paying the processing fee when it comes to cryptocurrency transactions. Is it the sender, the receiver, or perhaps a shared responsibility? How does the decision on who pays the fee impact the efficiency and security of the transaction? Understanding the answer to this question is crucial for making informed decisions in the world of cryptocurrency trading and investing.